[PATCH v3 07/35] x86/bugs: Restructure rfds mitigation

David Kaplan
2025-01-08T20:25:45Z

Restructure rfds mitigation to use select/update/apply functions to
create consistent vulnerability handling.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
---
arch/x86/kernel/cpu/bugs.c | 33 ++++++++++++++++++++++++++-------
1 file changed, 26 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index a8da097ab2d5..871b9f93b714 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -70,6 +70,9 @@ static void __init taa_apply_mitigation(void);
static void __init mmio_select_mitigation(void);
static void __init mmio_update_mitigation(void);
static void __init mmio_apply_mitigation(void);
+static void __init rfds_select_mitigation(void);
+static void __init rfds_update_mitigation(void);
+static void __init rfds_apply_mitigation(void);
static void __init srbds_select_mitigation(void);
static void __init l1d_flush_select_mitigation(void);
static void __init srso_select_mitigation(void);
@@ -193,6 +196,7 @@ void __init cpu_select_mitigations(void)
mds_select_mitigation();
taa_select_mitigation();
mmio_select_mitigation();
+ rfds_select_mitigation();
md_clear_select_mitigation();
srbds_select_mitigation();
l1d_flush_select_mitigation();
@@ -211,10 +215,12 @@ void __init cpu_select_mitigations(void)
mds_update_mitigation();
taa_update_mitigation();
mmio_update_mitigation();
+ rfds_update_mitigation();

mds_apply_mitigation();
taa_apply_mitigation();
mmio_apply_mitigation();
+ rfds_apply_mitigation();
}

/*
@@ -607,9 +613,6 @@ static int __init mmio_stale_data_parse_cmdline(char *str)
}
early_param("mmio_stale_data", mmio_stale_data_parse_cmdline);

-#undef pr_fmt
-#define pr_fmt(fmt) "Register File Data Sampling: " fmt
-
static const char * const rfds_strings[] = {
[RFDS_MITIGATION_OFF] = "Vulnerable",
[RFDS_MITIGATION_VERW] = "Mitigation: Clear Register File",
@@ -627,11 +630,28 @@ static void __init rfds_select_mitigation(void)

if (rfds_mitigation == RFDS_MITIGATION_AUTO)
rfds_mitigation = RFDS_MITIGATION_VERW;
+}

- if (x86_arch_cap_msr & ARCH_CAP_RFDS_CLEAR)
+static void __init rfds_update_mitigation(void)
+{
+ if (!boot_cpu_has_bug(X86_BUG_RFDS) || cpu_mitigations_off())
+ return;
+
+ if (verw_mitigation_enabled())
+ rfds_mitigation = RFDS_MITIGATION_VERW;
+
+ if (rfds_mitigation == RFDS_MITIGATION_VERW) {
+ if (!(x86_arch_cap_msr & ARCH_CAP_RFDS_CLEAR))
+ rfds_mitigation = RFDS_MITIGATION_UCODE_NEEDED;
+ }
+
+ pr_info("Register File Data Sampling: %s\n", rfds_strings[rfds_mitigation]);
+}
+
+static void __init rfds_apply_mitigation(void)
+{
+ if (rfds_mitigation == RFDS_MITIGATION_VERW)
setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
- else
- rfds_mitigation = RFDS_MITIGATION_UCODE_NEEDED;
}

static __init int rfds_parse_cmdline(char *str)
@@ -704,7 +724,6 @@ static void __init md_clear_update_mitigation(void)

static void __init md_clear_select_mitigation(void)
{
- rfds_select_mitigation();

/*
* As these mitigations are inter-related and rely on VERW instruction
--
2.34.1